Capturing the coolness

The coldest moment in my part of Cambridge recently was at 6.50 on the morning of Dec 19th, when the temperature in my back garden reached -10.5 deg C. Phawww!… Pretty chilly for here…

I know this interesting fact because one of last year’s toys was a Hobo Datalogger and an external temperature probe, which I bought because I suspected the thermostat on my hot water boiler of misbehaving. It wasn’t – but there are all sorts of situations where it’s quite fun to be able to record temperatures over an extended period.

The Hobo’s a lovely device, not much bigger than a matchbox, and you can configure it to capture data over a specified time period and at a particular frequency, and it’ll run almost for ever on a very small battery.

Click for a bigger version.

I hesitated for a while because I didn’t feel like paying for the HOBOware software, which, even in its ‘lite’ variety, costs 40 quid. It seemed like a lot when all I wanted was a list of numbers: why couldn’t they just let me get at the raw data? But I have to admit it does its job rather well, and it lets you configure the unit and navigate around any graphs produced. Also, I realised, the output of some of the sensor devices is not linear, so it’s doing rather more than simply recording voltages.

The unit I bought has built-in humidity and temperature detectors, and sockets where you can plug in a couple of other sensors – my external probe let me record the temperature both inside the studio and outside. I’m now trying to resist buying accessories like current clamps, which would let me record the power going to the under-floor heating system…

All in all, a fun toy.

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Aha – it’s definitely that time of year again. Nice looking (but relatively expensive) bit of kit.

I’ve been investigating the DIY approach and have just ordered a JeeNode and some other fun bits from the worderful JeeLabs – Ken at says that the JeeNode uses the same wireless module as the CurrentCost. Now that might open some possibilities…

Ah – hadn’t come across Jeelabs – a very nice site…

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